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[Qemu-devel] [PATCH 08/11] migration: implement bdrv_all_find_vmstate_bs
From: |
Denis V. Lunev |
Subject: |
[Qemu-devel] [PATCH 08/11] migration: implement bdrv_all_find_vmstate_bs and bdrv_unlock helpers |
Date: |
Wed, 4 Nov 2015 20:19:39 +0300 |
bdrv_all_find_vmstate_bs will return locked BlockDriverState. The code
written in the way to avoid nested locking taking into account that
patch for locking inside qemu_fopen_bdrv/qemu_fclose is acceptable.
Signed-off-by: Denis V. Lunev <address@hidden>
CC: Juan Quintela <address@hidden>
CC: Stefan Hajnoczi <address@hidden>
CC: Kevin Wolf <address@hidden>
---
block/snapshot.c | 21 +++++++++++++++++++++
include/block/snapshot.h | 3 +++
migration/savevm.c | 23 ++++++++---------------
3 files changed, 32 insertions(+), 15 deletions(-)
diff --git a/block/snapshot.c b/block/snapshot.c
index bb3bfd5..e196c9b 100644
--- a/block/snapshot.c
+++ b/block/snapshot.c
@@ -446,3 +446,24 @@ int bdrv_all_find_snapshot(const char *name,
BlockDriverState **first_bad_bs)
*first_bad_bs = bs;
return err;
}
+
+BlockDriverState *bdrv_all_find_vmstate_bs(void)
+{
+ BlockDriverState *bs = NULL;
+
+ while ((bs = bdrv_next(bs))) {
+ AioContext *ctx = bdrv_get_aio_context(bs);
+
+ aio_context_acquire(ctx);
+ if (bdrv_can_snapshot(bs)) {
+ return bs;
+ }
+ aio_context_release(ctx);
+ }
+ return NULL;
+}
+
+void bdrv_unlock(BlockDriverState *bs)
+{
+ aio_context_release(bdrv_get_aio_context(bs));
+}
diff --git a/include/block/snapshot.h b/include/block/snapshot.h
index 44c3a38..1f45f51 100644
--- a/include/block/snapshot.h
+++ b/include/block/snapshot.h
@@ -88,4 +88,7 @@ int bdrv_all_delete_snapshot(const char *name,
BlockDriverState **first_bsd_bs,
int bdrv_all_goto_snapshot(const char *name, BlockDriverState **first_bsd_bs);
int bdrv_all_find_snapshot(const char *name, BlockDriverState **first_bad_bs);
+BlockDriverState *bdrv_all_find_vmstate_bs(void);
+void bdrv_unlock(BlockDriverState *bs);
+
#endif
diff --git a/migration/savevm.c b/migration/savevm.c
index dbcb313..9339f2e 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -1237,17 +1237,6 @@ out:
return ret;
}
-static BlockDriverState *find_vmstate_bs(void)
-{
- BlockDriverState *bs = NULL;
- while ((bs = bdrv_next(bs))) {
- if (bdrv_can_snapshot(bs)) {
- return bs;
- }
- }
- return NULL;
-}
-
void hmp_savevm(Monitor *mon, const QDict *qdict)
{
BlockDriverState *bs, *bs1;
@@ -1293,8 +1282,8 @@ void hmp_savevm(Monitor *mon, const QDict *qdict)
sn->date_nsec = tv.tv_usec * 1000;
sn->vm_clock_nsec = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
- bs = find_vmstate_bs();
- if (!bs) {
+ bs = bdrv_all_find_vmstate_bs();
+ if (bs == NULL) {
monitor_printf(mon, "No block device can accept snapshots\n");
goto the_end;
}
@@ -1312,6 +1301,7 @@ void hmp_savevm(Monitor *mon, const QDict *qdict)
localtime_r((const time_t *)&tv.tv_sec, &tm);
strftime(sn->name, sizeof(sn->name), "vm-%Y%m%d%H%M%S", &tm);
}
+ bdrv_unlock(bs);
/* save the VM state */
f = qemu_fopen_bdrv(bs, 1);
@@ -1395,7 +1385,7 @@ int load_vmstate(const char *name)
return ret;
}
- bs_vm_state = find_vmstate_bs();
+ bs_vm_state = bdrv_all_find_vmstate_bs();
if (!bs_vm_state) {
error_report("No block device supports snapshots");
return -ENOTSUP;
@@ -1403,6 +1393,8 @@ int load_vmstate(const char *name)
/* Don't even try to load empty VM states */
ret = bdrv_snapshot_find(bs_vm_state, &sn, name);
+ bdrv_unlock(bs_vm_state);
+
if (ret < 0) {
return ret;
} else if (sn.vm_state_size == 0) {
@@ -1464,13 +1456,14 @@ void hmp_info_snapshots(Monitor *mon, const QDict
*qdict)
int total;
int *available_snapshots;
- bs = find_vmstate_bs();
+ bs = bdrv_all_find_vmstate_bs();
if (!bs) {
monitor_printf(mon, "No available block device supports snapshots\n");
return;
}
nb_sns = bdrv_snapshot_list(bs, &sn_tab);
+ bdrv_unlock(bs);
if (nb_sns < 0) {
monitor_printf(mon, "bdrv_snapshot_list: error %d\n", nb_sns);
return;
--
2.5.0
- Re: [Qemu-devel] [PATCH 02/11] snapshot: return error code from bdrv_snapshot_delete_by_id_or_name, (continued)
- [Qemu-devel] [PATCH 01/11] snapshot: create helper to test that block drivers supports snapshots, Denis V. Lunev, 2015/11/04
- [Qemu-devel] [PATCH 04/11] snapshot: create bdrv_all_goto_snapshot helper, Denis V. Lunev, 2015/11/04
- [Qemu-devel] [PATCH 07/11] migration: reorder processing in hmp_savevm, Denis V. Lunev, 2015/11/04
- [Qemu-devel] [PATCH 05/11] snapshot: create bdrv_all_find_snapshot helper, Denis V. Lunev, 2015/11/04
- [Qemu-devel] [PATCH 08/11] migration: implement bdrv_all_find_vmstate_bs and bdrv_unlock helpers,
Denis V. Lunev <=
- [Qemu-devel] [PATCH 09/11] migration: add missed aio_context_acquire for state writing/reading, Denis V. Lunev, 2015/11/04
- [Qemu-devel] [PATCH 06/11] migration: drop find_vmstate_bs check in hmp_delvm, Denis V. Lunev, 2015/11/04
- [Qemu-devel] [PATCH 11/11] monitor: add missed aio_context_acquire into vm_completion call, Denis V. Lunev, 2015/11/04
- [Qemu-devel] [PATCH 10/11] snapshot: create bdrv_all_create_snapshot helper, Denis V. Lunev, 2015/11/04
- Re: [Qemu-devel] [PATCH 2.5 v5 0/11] dataplane snapshot fixes, Stefan Hajnoczi, 2015/11/06